1. Field of the Invention
The present invention relates to ground surface covers, including devices and methods employed to reduce the erosion of levees and shorelines from wave action and currents, and more particularly to erosion control devices which are anchored into the soil to form a continuous mat parallel to the shoreline.
2. Description of Related Art
In the United States and other countries, miles of shorelines, beaches, and levees are annually subjected to severe erosion which literally washes away earth and exposes higher ground and valuable property to wave action and flooding. The problem is particularly of concern to residences and industries located near vital waterways bounded by levee systems, such as the Mississippi River and its tributaries. If left unchecked, wave and current action erodes and undermines the foundation of levees, leading to a weakening and ultimate failure of such levees during times of high water or storm surge.
Currently, commonly used methods of effectively controlling erosion involve the placement of a ground cover on top of and along the surface of interest, of an area extending the region of desired erosion control. The main objective of placing ground cover is to adequately control or minimize the movement of earthy or rock material along the surface of the ground, whatever the cause of the movement. In terms of functionality, there are several important properties for a ground surface cover system to have in order to be effective. Foremost, an effective ground surface cover system needs to be made of sufficient strength and long term stability to withstand one or more of the elements causing erosion processes such as wave action and current flow over long periods of time.
Several different types of ground surface cover systems are in common use. In addition to partially or completely covering the selected area of ground surface requiring erosion control with a multitude of removable individual elements, four main categories are ordinarily referred to with respect to ground surface cover systems, i.e., single cast structures, multi-cast structures, ‘gabion’ structures, and combination structures. Single cast ground surface cover systems are based on permanently covering the selected area of ground surface requiring erosion control with a layer of concrete alone, or, with a layer of concrete containing a dispersion of stones. Optional metal reinforcements internal to the cover material may be used throughout selected portions of the ground surface cover system. Multi-cast ground surface cover systems are based on the placement of a multitude of removable individual geometrically formed elements or blocks usually made from concrete, which partially or incompletely cover the selected area of ground surface requiring erosion control. Gabion ground surface cover systems are based on the placement of gabion structures, featuring a continuous or discontinuous network or web like structured system of metal baskets or cages of specified geometries, dimensions, and rigidity, filled with a chosen density of loose, non-cemented stones. Combination ground surface cover systems are based on the placement of a plastic matting featuring concrete casting modules, typically of a honeycomb like geometry, upon the ground, and casting, on-site, the concrete modules. Individual concrete modules are relatively near to, but are not in contact with, each other.
Multi-cast ground surface cover systems may be further classified into two different types, i.e., systems based on interconnecting elements or locks, and systems based on interlocking elements or blocks. Hereinafter, “interconnecting” refers to the state or configuration of elements or blocks placed side-to-side or adjacent to each other, thereby forming a larger non-flexible pattern of such elements or blocks, where the elements or blocks are connected, and not locked, even loosely, to each other via element to element or block to block male to female connection or mating of any sort. Hereinafter, “interlocking” refers to the state or configuration of elements or blocks which are placed in contact with each other via some sort of element to element or block to block male to female interlocking connection or mating, thereby forming a larger non-flexible or flexible pattern of such elements or blocks, where the elements or blocks are locked to each other. In this case, the interlocking connection or mating between any two elements or blocks forms a joint, where the joint is comprised of a male component structural feature such as a hook, protrusion, extension, barb, tongue, or nose, compatible with and interlocked to a corresponding female component structural feature such as a recess, opening, or related cutout structural feature. According to present usage, an interlocking element to element or block to block joint may be non-flexible or flexible, whereby flexibility refers to the capability of movement or turning in a horizontal or vertical direction without damaging or breaking the interlocking joint, or the elements or blocks.
In regard to multi-cast ground surface cover systems, current teachings of interlocking ground surface cover systems are based on individual elements interlocked by rigid or fixed, non-flexible joints between the elements, resulting in no degrees of freedom for vertical or horizontal movement. This characteristic of multi-cast interlocking element systems presents several significant limitations for application of such systems to erosion control, not the least of which are the tediousness of installation of great numbers of small elements to one another, and the difficulty of removing and replacing individual elements over time.
An ideal ground surface cover system for effective erosion control would feature all the above mentioned properties and attributes necessary for achieving the objective of adequately controlling or minimizing ground movement during a potential erosion process, including high strength and long term stability, flexible adjustment to ground movement, economic and feasible manufacturing and installation, replaceability, and reusability. It will be shown that incorporating the feature of flexibility into a ground surface cover system leads to significantly better achievement of having all of these properties and attributes of an effective erosion control system.